T-cell receptor Valpha spectratype analysis of a CD4-mediated T-cell response against minor histocompatibility antigens involved in severe graft-versus-host disease

Advances in single-cell sequencing: insights from organ transplantation

Single-cell RNA sequencing (scRNA-seq) is a comprehensive technical tool to analyze intracellular and intercellular interaction data by whole transcriptional profile analysis. Here, we describe the application in biomedical research, focusing on the immune system during organ transplantation and rejection. Unlike conventional transcriptome analysis, this method provides a full map of multiple cell populations in one specific tissue and presents a dynamic and transient unbiased method to explore the progression of allograft dysfunction, starting from the stress response to final graft failure. This promising sequencing technology remarkably improves individualized organ rejection treatment by identifying decisive cellular subgroups and cell-specific interactions.

Recipient-specific T-cell repertoire reconstitution in the gut following murine hematopoietic cell transplant

Graft-versus-host disease (GVHD) is a complication of hematopoietic cell transplantation (HCT) caused by alloreactive T cells. Murine models of HCT are used to understand GVHD and T-cell reconstitution in GVHD target organs, most notably the gastrointestinal (GI) tract where the disease contributes most to patient mortality. T-cell receptor (TCR) repertoire sequencing was used to measure T-cell reconstitution from the same donor graft (C57BL/6 H-2b) in the GI tract of different recipients across a spectrum of matching, from syngeneic (C57BL/6), to minor histocompatibility (MHC) antigen mismatch BALB.B (H-2b), to major MHC mismatched B10.BR (H-2k) and BALB/c (H-2d). Although the donor T-cell pools had highly similar TCR, the TCR repertoire after HCT was very specific to recipients in each experiment independent of geography. A single invariant natural killer T clone was identifiable in every recipient group and was enriched in syngeneic recipients according to clonal count and confirmatory flow cytometry. Using a novel cluster analysis of the TCR repertoire, we could classify recipient groups based only on their CDR3 size distribution or TCR repertoire relatedness. Using a method for evaluating the contribution of common TCR motifs to relatedness, we found that reproducible sets of clones were associated with specific recipient groups within each experiment and that relatedness did not necessarily depend on the most common clones in allogeneic recipients. This finding suggests that TCR reconstitution is highly stochastic and likely does not depend on the evaluation of the most expanded TCR clones in any individual recipient but instead depends on a complex polyclonal architecture.

[Cutaneous graft-versus-host disease]

BACKGROUND

Graft-versus-host disease (GvHD) is a complex multiorgan disease, which can occur as a complication following allogeneic stem cell transplantation. Involvement of the skin represents the most common appearance of GvHD. The role of the dermatologist is critical for diagnosis and initiation of treatment.

OBJECTIVES

The aim of this article is to provide a comprehensive review of the cutaneous types of GvHD and to present the most recent data on diverse therapy options for its acute and chronic form allowing the clinician to establish a definite diagnosis and to initiate proper therapy.

MATERIALS AND METHODS

Possible clinical appearances and recommended criteria to assist in making the right diagnosis are presented by means of expert recommendations.

RESULTS AND CONCLUSION

GvHD is still a complex entity whose diagnosis is often associated with challenges due to its variable presentation. Proper diagnosis and subsequent therapy is paramount for the optimal clinical outcome.

Cutaneous Graft-Versus-Host Disease: Diagnosis and Treatment

Graft-versus-host disease (GVHD) is an immunological reaction and a frequent complication following allogeneic hematopoietic stem cell transplantation. It is associated with high mortality rates and may have a significant negative impact on the patient's quality of life, particularly in the chronic-stage setting. Many different organs can be involved, which leads to a wide range of clinical manifestations. In this context, dermatologists play a key role by diagnosing and treating GVHD from the outset since cutaneous features are not just the most common but are also usually the presenting sign. Several skin-direct therapies are available and may be indicated as monotherapy or adjuvant treatment in order to allow faster tapering and withdrawal of systemic immunosuppression. Treatment of steroid-refractory patients remains a challenge and, to date, no consensus has been reached for one single agent in second-line therapy. This article aims to review skin involvement as well as provide and update discussion on therapeutic options for both acute and chronic cutaneous GVHD.

Breakdown of immune privilege and spontaneous autoimmunity in mice expressing a transgenic T cell receptor specific for a retinal autoantigen

Despite presence of circulating retina-specific T cells in healthy individuals, ocular immune privilege usually averts development of autoimmune uveitis. To study the breakdown of immune privilege and development of disease, we generated transgenic (Tg) mice that express a T cell receptor (TCR) specific for interphotoreceptor retinoid-binding protein (IRBP), which serves as an autoimmune target in uveitis induced by immunization. Three lines of TCR Tg mice, with different levels of expression of the transgenic R161 TCR and different proportions of IRBP-specific CD4⁺ T cells in their peripheral repertoire, were successfully established. Importantly, two of the lines rapidly developed spontaneous uveitis, reaching 100% incidence by 2 and 3 months of age, respectively, whereas the third appeared "poised" and only developed appreciable disease upon immune perturbation. Susceptibility roughly paralleled expression of the R161 TCR. In all three lines, peripheral CD4⁺ T cells displayed a naïve phenotype, but proliferated in vitro in response to IRBP and elicited uveitis upon adoptive transfer. In contrast, CD4⁺ T cells infiltrating uveitic eyes mostly showed an effector/memory phenotype, and included Th1, Th17 as well as T regulatory cells that appeared to have been peripherally converted from conventional CD4⁺ T cells rather than thymically derived. Thus, R161 mice provide a new and valuable model of spontaneous autoimmune disease that circumvents the limitations of active immunization and adjuvants, and allows to study basic mechanisms involved in maintenance and breakdown of immune homeostasis affecting immunologically privileged sites such as the eye.

Induction of acute GVHD by sex-mismatched H-Y antigens in the absence of functional radiosensitive host hematopoietic-derived antigen-presenting cells

It is currently thought that acute GVHD cannot be elicited in the absence of Ag presentation by radiosensitive host hematopoietic-derived APCs after allogeneic BM transplantation. Because clinical data suggest that sex-mismatched H-Y Ags may be important minor histocompatibility Ags for GVH responses, we directly tested their relevance and ability to initiate GVHD when presented by either the hematopoietic- (host or donor) or the nonhematopoietic-derived APCs. H-Y minor Ag incompatibility elicited both CD4(+) and CD8(+) T-cell driven GVHD lethality. Studies with various well-established BM chimera recipients, in contrast to the current views, have reported that in the absence of functional radiosensitive host hematopoietic-derived APCs, H-Y Ag presentation by either the donor hematopoietic-derived or the host nonhematopoietic-derived APCs is sufficient for inducing GVHD. Our data further suggest that infusion of sufficient numbers of alloreactive donor T cells will induce GVHD in the absence of radiosensitive host hematopoietic-derived APCs.

Uneven colonization of the lymphoid periphery by T cells that undergo early TCR{alpha} rearrangements

A sparse population of thymocytes undergoes TCRalpha gene rearrangement early in development, before the double-positive stage. The potential of these cells to contribute to the peripheral T cell pool is unknown. To examine the peripheral T cell compartment expressing a repertoire biased to early TCR gene rearrangements, we developed a mouse model in which TCRalpha rearrangements are restricted to the double-negative stage of thymocyte development. These mice carry floxed RAG2 alleles and a Cre transgene driven by the CD4 promoter. As expected, conventional T cell development is compromised in such Cre(+) RAG2(fl/fl) mice, and the TCRalphabeta(+) T cells that develop are limited in their TCRalpha repertoire, preferentially using early rearranging Valpha genes. In the gut, the Thy-1(+)TCRalphabeta(+) intraepithelial lymphocyte (IEL) compartment is surprisingly intact, whereas the Thy-1(-)TCRalphabeta(+) subset is almost completely absent. Thus, T cells expressing a TCRalpha repertoire that is the product of early gene rearrangements can preferentially populate distinct IEL compartments. Despite this capacity, Cre(+) RAG2(fl/fl) T cell progenitors cannot compete with wild-type T cell progenitors in mixed bone marrow chimeras, suggesting that in normal mice, there is only a small contribution to the peripheral T cell pool by cells that have undergone early TCRalpha rearrangements. In the absence of wild-type competitors, aggressive homeostatic proliferation in the IEL compartment can promote a relatively normal Thy-1(+) TCRalphabeta(+) T cell pool from the limited population derived from Cre(+) RAG2(fl/fl) progenitors.

Overlap between in vitro donor antihost and in vivo posttransplantation TCR Vbeta use: a new paradigm for designer allogeneic blood and marrow transplantation

Following allogeneic blood and marrow transplantation (BMT), mature donor T cells can enhance engraftment, counteract opportunistic infections, and mount graft-versus-tumor (GVT) responses, but at the risk of developing graft-versus-host disease (GVHD). With the aim of separating the beneficial effects of donor T cells from GVHD, one approach would be to selectively deplete subsets of alloreactive T cells in the hematopoietic cell inoculum. In this regard, TCR Vbeta repertoire analysis by CDR3-size spectratyping can be a powerful tool for the characterization of alloreactive T-cell responses. We investigated the potential of this spectratype approach by comparing the donor T-cell alloresponses generated in vitro against patient peripheral blood lymphocytes (PBLs) with those detected in vivo posttransplantation. The results indicated that for most Vbeta families that exhibited alloreactive CDR3-size skewing, there was a robust overlap between the in vitro antipatient and in vivo spectratype histograms. Thus, in vitro spectratype analysis may be useful for determining the alloreactive T-cell response involved in GVHD development and, thereby, could serve to guide select Vbeta family depletion for designer transplants to improve outcomes.

T-cell receptor V(alpha) usage by effector CD4+Vbeta11+ T cells mediating graft-versus-host disease directed to minor histocompatibility antigens

T-cell receptor (TCR) Valpha (TRAV) and Vbeta (TRBV) chains provide the T-cell specificity for recognition of major histocompatibility complex (MHC)-bound antigens. However, there is limited information on the diversity of TRAV use within an antigen response. Previous investigation of CD4(+) T-cell-mediated graft-versus-host disease (GVHD) in the minor histocompatibility antigen-mismatched C57BL/6 (B6)-->BALB.B irradiated murine model determined that Vbeta11(+) T cells were associated with disease severity. Polymerase chain reaction (PCR)-based complementarity-determining region 3 (CDR3)-sized spectratype analysis of B6 Vbeta11(+) T cells from the spleens of recipient BALB.B mice undergoing GVHD indicated biased use within the V(alpha)6, 9, 13, 14, 18, and 22 families. To probe deeper into this limited V(alpha) response, the current study was undertaken to further define TRAV-Jalpha (TRAJ) nucleotide sequences found in host-presensitized B6 Vbeta11(+) T cells proliferating in response to in vitro stimulation with BALB.B splenocytes. Using the nonpalindromic adaptor PCR method, we found dominant use of the TRAV13-TRAJ16 transcript combination. Then, using laser capture microdissection, we found use of the identical TRAV-TRAJ nucleotide sequence in areas dominated by infiltrating Vbeta11(+) CD4(+) T cells during the development of GVHD in both the rete-like prominences of the dorsal lingual epithelium and the ileal crypts of the small intestine.